Angiotensin-converting-enzyme (ACE) inhibitors have been shown to reduce morbidity and mortality in patients with chronic heart failure and systolic left ventricular dysfunction as well as in patients post myocardial infarction. (See The CONSENSUS Trial Study Group. Effects of enalapril on mortality in severe congestive heart failure. Results of the Cooperative North Scandinavian Enalapril Survival Study (CONSENSUS). N Engl J Med 1987; 316:1429-1435; The SOLVD Investigators. Effect of enalapril on survival in patients with reduced left ventricular ejection fractions and congestive heart failure. N Engl J Med 1991; 325: 293-302; The SOLVD Investigators. Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions. N Engl J Med 1992; 327: 685-691; Cohn J N, Johnson G, Ziesche S, et al. A comparison of enalapril with hydralazine-isosorbide dinitrate in the treatment of chronic congestive heart failure. N Engl J Med 1991; 325: 303-310; Pfeffer M A, Braunwald E, Moye L A, et al. on behalf of the SAVE Investigators. Effect of captopril on mortality and morbidity in patients with left ventricular dysfunction after myocardial infarction. Results of the Survival and Ventricular Enlargement Trial. N Engl J Med 1992; 327: 669-677; The Acute Infarction Ramipril Efficacy (AIRE) Study Investigators. Effect of ramipril on mortality and morbidity of survivors of acute myocardial infarction with clinical evidence of heart failure. Lancet 1993; 342: 812-828; Fonarow G C, Chelimsky-Fallick C, Warner Stevenson L, et al. Effect of direct vasodilation with hydralazine versus angiotensin-converting enzyme inhibition with captopril on mortality in advanced heart failure: the Hy-C trial. J Am Coll Cardiol 1992; 19: 842-850; Gruppo Italiano per lo Studio delia Sopravvivenza nell'infarto Miocardico. GISSI-3: Effects of lisinopril and transdermal glyceryl trinitrate singly and together on 6-week mortality and ventricular function after acute myocardial infarction. Lancet 1994; 343: 1115-1122; ISIS Collaborative Group OU. ISIS-4: Randomized study of oral isosorbide mononitrate in over 50,000 patients with suspected acute myocardial infarction. Circulation 1993; 88: 1394.) The benefits of ACE inhibitors have been attributed to blockade of angiotensin II production and/or to a decrease in the breakdown of bradykinin. (See Pitt B, Chang P, Timmermans P. Angiotensin II receptor antagonists in heart failure: Rationale and design of the Evaluation of Losartan in the Elderly (ELITE) Trial. Cardiovascular Drugs and Therapy 1995; 9: 693-700; and Gavras I. Bradykinin-mediated effects of ACE inhibition. Kidney Int 1992: 42: 1020-1029.) Bradykinin has been shown to have beneficial effects associated with the release of nitric oxide and prostacyclin which may contribute to the hemodynamic effects of ACE inhibition. Bradykinin may, however, also be responsible for certain adverse effects associated with use of ACE inhibitors, such as cough, angioedema, renal dysfunction, and hypotension. (See Pitt B, Chang P, Timmermans P. Angiotensin II receptor antagonists in heart failure: Rationale and design of the Evaluation of Losartan in the Elderly (ELITE) Trial. Cardiovascular Drugs and Therapy 1995; 9: 693-700; Gavras I. Bradykinin-mediated effects of ACE inhibition. Kidney Int 1992: 42: 1020-1029; Israili Z H, Hall W D. Cough and angioneurotic edema associated with angiotensin-converting enzyme inhibitor therapy. A review of the literature and pathophysiology. Ann Intern Med 1992; 117: 234-242; Chalmers D, Dombey S L, Lawson D H. Post-marketing surveillance of captopril (for hypertension): a preliminary report. Br J Clin Pharmacol 1987; 24: 343-349; Lacourciere Y, Brunner H, Irwin R, et al. and the Losartan Cough Study Group. Effects of modulators of the renin-angiotensin-aldosterone system on cough. J Hypertension 1994; 12: 1387-1393.) These adverse effects may account in part for the fact that ACE inhibitors are used in less than 30 percent of patients with heart failure in spite of their proven clinical benefit. (See Stafford R S, Saglam D, Blumenthal D. Low rates of angiotensin-converting enzyme inhibitor use in congestive heart failure. Circulation 1996; 94: I-194(Abstract)).
The development of orally-active, nonpeptidic angiotensin II type 1 receptor antagonists such as losartan, has provided the opportunity to block the angiotensin II type 1 receptor specifically without increasing bradykinin levels. (See Timmermans P, Wong P C, Chiu AT, et al. Angiotensin II receptors and angiotensin II receptor antagonists. Pharmacol Reviews 1993; 45: 205-251.) Since angiotensin II may be produced by alternate pathways, losartan may offer additional advantages over treatment with ACE inhibitors where blockade of the effects of angiotensin II may be incomplete. (See Miura S, Ideishi M, Sakai T, et al. Angiotensin II formation by an alternative pathway during exercise in humans. J Hypertension 1994; 12: 1177-1181; Urata H, Kinoshita A, Misono K S, Bumpus F M, Husain A. Identification of a highly specific chymase as the major angiotensin II-forming enzyme in the human chymase. J Biol Chem 1990; 265: 22348-22357; Urata H, Strobel F, Ganten D. Widespread tissue distribution of human chymase. J Hypertension 1994; 12: S17-S22; Aldigier J C, Huang H, Dalmay F, et al. Angiotensin-converting enzyme inhibition does not suppress plasma angiotensin II increase during exercise in humans. J Cardiovasc Pharmacol 1993; 21: 289-295.) Losartan is indicated for the treatment of hypertension in many countries and in earlier studies in patients with symptomatic heart failure, oral losartan produced beneficial hemodynamic effects both acutely and with chronic dosing. (See Crozier I, Ikram H, Awan N, et al. Losartan in heart failure: Hemodynamic effects and tolerability. Circulation 1995; 91: 691-697; and Gottlieb S S, Dickstein K, Fleck E, et al. Hemodynamic and neurohormonal effects of the angiotensin II antagonist losartan in patients with congestive heart failure. Circulation 1993; 88: 1602-1609.)
The Evaluation of Losartan In The Elderly (ELITE) Study was conducted to compare effects on renal function, morbidity/martality, and tolerability of long-term treatment with losartan versus captopril, in older patients with symptomatic heart failure.
An ELITE substudy focused on analyzing the electrocardiograms that were collected at the start and end of the study in a subset of patients. The data from this substudy shows that QT dispersion increased during the 48 weeks of the study with captopril treatment whereas a reduction in QT dispersion or inhibition of the progression of QT dispersion was observed with losartan treatment. QT dispersion is a reflection of regional variation in ventricular repolarization and is a strong predictor of ventricular arrhythmias and death. Effects of losartan on QT dispersion may explain the observed reduction in mortality and sudden cardiac death with losartan treatment versus captopril in the ELITE study.